A conventional vehicle frame assembly typically comprises a main frame part and separate front and rear frame parts secured to the main frame part. The main frame part includes laterally spaced side sills, which are the main structural member between the front and rear wheels, and the rear frame part includes laterally spaced rear frame members that are joined to the side sills. The known vehicle frame assembly achieves an improvement in rigidity as a result of joining the side sills to the rear frame members such that each combination forms a substantially continuous frame member along a longitudinal direction of the vehicle frame assembly. However, the conventional rear frame to side sill joint only provides engagement on inboard walls of the respective side sill and rear frame member, and this can affect load transfer along the outboard sidewalls between the side sill and the rear frame member. Because the rear frame member is the primary load path for rear collisions, as well as the primary rear structure for suspension inputs into the vehicle body, it is necessary for the rear frame member to have a strong connecting to the side sill.